Seismic Fragility Analysis of Subway Station Structures Based on Shaking Table Tests and IDA

To evaluate the seismic performance and fragility of subway station structures, a subway station in the Xi’an region is selected as the engineering background. A combined approach integrating shaking table tests, finite element (FE) simulations, and incremental dynamic analysis (IDA) is employed to investigate the dynamic response and seismic fragility of the structure. A finite element model considering soil–structure interaction (SSI) is developed and validated against shaking table test results. The peak ground acceleration (PGA) at the foundation base is adopted as the seismic intensity measure, and the inter-story drift ratio (IDR) is used as the engineering demand parameter to establish the fragility model. The effects of ground motion type and concrete strength on seismic fragility are further analyzed. Results show that structural acceleration increases with height and ground motion intensity, while near-field ground motions induce more pronounced displacement responses. Base PGA exhibits the highest correlation and lowest dispersion with structural demand, making it the optimal intensity measure. Fragility curves follow a typical S-shaped trend with increasing PGA. Near-field motions significantly increase structural vulnerability, whereas higher concrete strength effectively reduces fragility. The findings provide a reference for seismic performance assessment and design of subway station structures.